The use of input capacitors as isolation elements in transformerless a.c.-to-d.c. converters is well known. Bereskin (U.S. Pat. No. 3,001,120), for example, shows the use of such capacitors. His circuit, however, requires the use of surge resistors and nonpolarized capacitors.
In an article by J. Saia, "Transformerless Phase Controlled Power Supply," IBM Technical Disclosure Bulletin, Vol. 13, No. 10, March 1971, pp. 3179-3180, a transformerless a.c.-to-d.c. power supply is shown.
Other references showing the use of input isolation capacitors in a.c.-to-d.c. converters are U.S. Pat. Nos. 3,286,171 (Fluegel et al.) and 3,942,095 (Togneri et al.).
None of these prior art references, however, show or suggest the manner by which polarized capacitors could be used in the a.c. input circuit.
The purpose of the present invention is to use polarized input isolation capacitors which can be of large enough value to provide surge limitations that required large, heat-dissipating resistors in the prior art.